"O'" is a prefix commonly used in names, particularly in Irish and Scottish cultures. It signifies "descendant of" and is often followed by a family name, indicating lineage. For example, the name O'Reilly means "descendant of Reilly." In addition to its genealogical significance, "O'" is also a stylistic element in names that adds a sense of heritage and identity. It reflects the importance of ancestry in Irish and Scottish traditions, where family connections are highly valued.